Membrane probe for taking samples of an analyte located in a fluid medium

ABSTRACT

The inventive prove ( 10 ) for taking samples of an analyte located in the fluid medium has a membrane which closes the probe ( 10 ) to the outside and which is permeable to the analyte, a flow-through cell which is configured behind the membrane, a probe part ( 14 ) with at least one incoming line and one outgoing line leading to or from the flow-through cell, and a membrane holder ( 160 ) which, together with the membrane, forms a replaceable unit of the probe part ( 14 ) together with the incoming line and outgoing line.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention concerns a probe for taking samples of an analyte locatedin the fluid medium, the probe including a membrane which closes theprobe to the outside, the membrane being permeable to the analyte, aflow-through cell positioned behind the membrane, and at least oneincoming and outgoing line leading to or from the flow-through cell.

2. Description of The Related Art

In chemical analysis it is frequently desired that particular componentsof a system are detected or monitored and that this occurs via ameasurement probe. To this end various probes are in use, each designeddepending upon the particularities of the various analyticalpossibilities. For example, probes are known which contain electrodes orpolarographic sensors and which are closed off towards the outside—thatis, with respect to the medium being analyzed—by a membrane. Such probescontain, among other things, a stationary fluid, such as an electrolyteor a buffer solution. Further, it is known to have probes formeasurement using a flow-through process, that is, that the substance tobe analyzed (the analyte), after passing through the membrane andentring into the probe, is transported to a remote measuring system fortaking measurements.

In DE-AS 26 50 730 B1 and WO 97/08533 A2 a submerged dialyzer isdescribed, in which a membrane is applied directly upon a replaceableprobe part, which includes an incoming and outgoing line. The membraneis so tensioned over the head of the probe part, that it is removable.In order to guarantee an even distribution of the buffer under themembrane, ruffles or ridges are provided in the head of the probe part.Since the membrane is frequently very thin and sensitive, changing outof the membrane, and cupping of the membrane over the head, is quitedifficult. Besides, the exchange surface between the fluid mediumsituated outside of the membrane and the medium flowing through theridges is relatively large and unspecified.

In DE-OS 2 310 264 a similar probe is described, in which the incomingand outgoing lines are wound in the form of a helix.

In EP 0 054 537 A1 a probe carrier is described, in which the membraneis applied directly upon the probe carrier. The arrangement is soprovided on a housing, that the membrane cannot be replaced in a simplemanner. Besides this, the exchange surface over the flow-through cellcannot be varied.

In DE 297 01 652 U1 a probe is described, in which a membrane is laidupon the probe part and is secured from the outside using a membraneholder. The membrane holder has a defined opening, so that a fluidmedium can pass through the opening to the membrane and from this to aflow-through cell. The exchange surface between the membrane and theflow-through cell is determined by a through-hole, which is situatedbehind the membrane in the probe part. Since the membrane is clampedbetween the probe part and the membrane holder, the replacement of themembrane is difficult. Besides this, the exchange surface area ispermanently predetermined by the probe and cannot be varied.

A similar probe is described in DE-OS 31 26 648 A1, in which themembrane is introduced in the opening of a membrane holder which can bescrewed upon the probe. Thereby the problem occurs, that the membranesurface towards outside is predetermined by the through-hole in themembrane holder, which at the same time determines the exchange surface.

In WO 96/07885 A1 a probe with a circular shaped surface is described,in which a membrane is glued directly upon a membrane holder, andwherein a communication channel for an incoming and an outgoing line isprovided between the membrane and the membrane holder. The probe has thedisadvantage, that the membrane is not easy to replace and is adhered.It cannot be employed in extreme environmental conditions, since anadhesive bond in this form cannot be made sterile-tight and woulddissolve or release during steam sterilization. Further, the membrane iscompletely open upwards and offers a maximal exchange surface.

The herein described probe type is suitable for taking samples from afluid medium, wherein the analyte comes into contact with an acceptor(medium) after entry into the probe, which via an incoming and outgoingline is channeled to a flow-through cell proved in the probe.

SUMMARY OF THE INVENTION

It is thus the task of the invention, to provide a probe, in which themembrane and the membrane holder are easy to replace and with which adefined exchange surface with the flow-through cell can easily bevaried, while using an otherwise identical or standard membrane. Theprobe should herein be capable of being employed in extreme analyteconditions, that is, should be sterilizable by steam and should besterile-tight.

The probe is to be so designed or equipped, that even minute amounts ofanalyte can be removed, and that sample volumes can be kept small,insofar as this is desired.

For solving this task provision is made to introduce the membranebetween two membrane seals and with these to form a unit, wherein themembrane seals respectively have a passage or through-hole to themembrane holder or as the case may be the probe part, and the unit isprovided between the membrane holder and the probe part and is securableto the probe part via the membrane holder in a replaceable yet sealingmanner. The membrane holder is in the form of a gland and provides, bymeans of the through-holes of the membrane seals, for only a definedlimited surface of the membrane to be exposed over the flow-throughcell.

It is thus proposed, that the membrane holder defines the exchangesurface over the flow-through cell. The membrane holder is therebypositioned before the membrane and the probe part and sealingly andreleaseably clamps the membrane tightly to the probe part. The membraneis provided between two membrane seals and forms thereby a sandwichstructure type unit, which is easily exchangeable and easy to manipulateand besides this has a good sealing effect. Thereby the membrane andmembrane holder are removable as a single unit, so that the exchangesurface can be changed by a simple unscrewing of the unit comprised ofmembrane and membrane holder and replaced by another unit dimensioned asneeded.

An elementary difference in comparison to the conventional probes iscomprised therein, that the membrane is provided tightly or fixedlybetween the membrane seals, so that the normally thin and sensitivemembrane can be exchanged together with the membrane seals, wherein thisunit and the membrane holders are premade.

The inventive probe is preferably a pure sample-taking probe; the actualmeasurement is undertaken in conventional manner outside of the probe,but it can however also occur within the flow-through cell. In the latercase the flow-through cell must be supplementally provided with at leastone sensor as well as circuits or conductors going to the sensor forcontrol of the measurement process and for relaying or communicating themeasurement results. These measures as such are known and are thus notdescribed in greater detail herein.

The measurement can occur via various measurement processes. If themeasurement is carried out outside of the probe, then there is throughthe conduits an acceptor flow directed to the flow-through cell which isclosed off to the outside via the membrane and subsequently flows out ofthe probe through the outgoing lines and is supplied to the measurementunit. The acceptor flow can be directed continuously through the probe.It is possible, to interrupt the acceptor flow, so that a definedenrichment of the analyte defusing through the membrane can occur in theacceptor. The control of the acceptor flow occurs however likewise fromoutside the probe and is thus not discussed in greater detail herein.

An important characteristic of the invention is comprised therein, thatthe membrane is connected to an isolated membrane holder.

The production or premanufacture of a unit comprised of membrane andmembrane holder offers many advantages. First, the unit comprised ofmembrane and membrane holder makes possible a simple exchange of themembrane with another membrane connected with an appropriate membraneholder. In this manner, used membranes can be easily changed andrespectively different membranes can be used selectively for variousmeasurement process and/or analytes using the same probe. Since themembrane is connected with the holder, the exchange of the frequentlythin and sensitive membrane is easy to accomplish. The membrane can forexample of adhered to the holder, or it can be secured to the holder viasuitable securing means.

A further important feature of the invention is comprised therein, thatthe membrane holder forms a gland and only a defined surface of themembrane (over the flow-through cell) is exposed as an exchange surface,through which the analyte can penetrate into the flow-through cell fromoutside. For the measurement and evaluation of the analyte it isimportant, that the exchange surface between the fluid medium originallycontaining the analyte and the acceptor situated in the flow-throughcell is precisely determinable, and that one can in certain casesexercise influence over this exchange surface.

The membrane holder is thus so designed, that a defined surface area ofthe membrane situated over the flow-through cell and connected therewithis exposed, through which the analyte can penetrate. It is thus possibleto have available various units of membrane and membrane holde forconducting various measurements in which the membrane holder exposesrespectively various surface areas with an otherwise identical membrane.

In a further development of the invention it is envisioned, that theflow-through cell within the probe has an elongate form along themembrane. The elongate form is a particularly suitable geometry for aflow-through measurement, since a discontinuous or interrupted flowprocess, with uniform-as-possible acceptor dwell times, can be achieved.Besides this it is useful, to maintain the acceptor below the membraneto a thin layer thickness.

The flow-through cell can—in one embodiment of the invention—be formedor designed having one channel introduced in the membrane and one in theseal which may in certain cases be associated therewith. Thereby it isoptimally achieved, that the acceptor medium during the course of theexchange or, as the case may be, the entry of analyte, occurs in a thinlayer directly along the membrane.

The incoming and outgoing lines can advantageously be provided on theback side of the elongated flow-through cell.

In an advantageous embodiment of the invention the incoming and outgoinglines are comprised of capillaries, between which the (preferablyelongate, channel-like) flow-through cell is provided.

It is further advantageous, that the probe as a whole is shaped like atube, wherein the flow-through cell and the unit comprised of membraneand membrane holder are provided on one end of the tube and wherein theincoming and outgoing lines lead to connections on the other end of thetube. Depending upon the selected length of this tube, the samplecollection—which occurs at the lower end of the tube by passage ofanalyte into the flow-through cell—can be positioned or located at thedesired point within the system to be examined. The probe can thus bedesigned to be both compact as well as long. The differences hereinwould essentially only be in the length of the incoming and outgoingchannels and the length of the probe body.

A unit comprised of membrane and membrane holder can, for example, bescrewed onto the probe. However, other coupling possibilities arepossible.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail onthe basis of the illustrative embodiment shown in the figures, which isintended to serve only for explaining the invention without limiting thescope of the invention in any way. In the drawings there is shown

FIG. 1: an illustrative embodiment of the inventive probe as a whole;

FIG. 2: a membrane holder for the probe of FIG. 1 shown for illustrativepurposes in various views or sections a), b), c);

FIG. 3: a membrane seal with slit like openings for the sameillustrative embodiment;

FIG. 4: the part of the probe for receiving the membrane of theembodiment shown in FIG. 1, without the membrane and the membraneholder, in various sections or views a), b), c);

FIG. 5: a cap-shaped cover for the illustrative embodiment of the probewith connections for the incoming and outgoing lines, in varioussectional views a) and b);

FIG. 6: an example for two different employment possibilities of theinventive probe in two different illustrative embodiments.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows the probe indicated overall with reference number 10 in alongitudinal section perpendicular to the plane in which the membraneextends. The illustrative embodiment of the probe 10 is comprised of asubmersion tube 12, a probe part 14 having a recess for receiving theunit comprised of a membrane and a membrane holder, which probe part isshown in greater detail in FIG. 4, the schematically represented unit 16comprised of membrane and membrane holder, which is shown in greaterdetail in FIG. 2, as well as connection cap 18 shown in FIG. 5. Thedetails of this illustrative embodiment of the probe are described ingreater detail below with reference to FIGS. 2 through 5.

FIG. 2 shows the membrane holder 160 in a sectional view a) orientedperpendicular to a not shown membrane, a view b) in the direction of thearrow R shown in FIG. 2a) and a transverse sectional view c), seen inthe direction of the arrows A—A from FIG. 2a). On the one side of themembrane holder 160, which in the assembled position lies flat againstthe probe part 14, a recess 162 is formed in, in which the membrane andin certain cases supplemental seals can be introduced. The through-holes164 serve for securing the membrane holder 160 to the probe part 14shown in FIGS. 1 and 4. On the opposite side of the membrane holder arecess 166 is milled or machined into the membrane holder 160, of whichthe floor area is here indicated with reference number 167. In thecenter of the recess 166 there is—in this embodiment correspondingapproximately with the floor area 167—a through hole 168. A gland isformed in the membrane holder 160 by the recess 166 and the through hole168, which exposes only a predetermined surface area of the membraneintroduced in the recess 162.

FIG. 3 shows a membrane seal 170, as it is introduced in the recess 162of the membrane holder 160 for sealing the membrane against the probepart 14 on the one hand and the membrane holder 160 on the other hand.The membrane seals 170, 170 a exhibit two circular through holes orpassageways 172, 172 a through which, in the assembled condition, thescrews can extend to the probe part 14 for securing the unit 16, and anelongated through hole 174, which is covered over by the through hole168 in the membrane holder. For sealing in the probe, a thin membrane,which could for example be comprised of a dialysis membrane, there isprovided in the here illustrated embodiment, that the membrane 150 inthe shape of a rectangle corresponding to the surface area of the recess162 is introduced between two membrane seals 170, 170 a shown in FIG. 3,and this sandwich structure is then introduced into the recess 162. Theseals 170, 170 a can be comprised for example of silicon. In theassembled position, the two membrane seals 170, 170 a seal the membrane150 on the one hand against the membrane holder 160, and on the otherhand against the probe part 14. Therein the through-hole 174, 174 a inthe membrane seal 170 lying against the membrane holder, together withthe through-hole 168 in the membrane holder 160, forms a gland whichexposes only a predetermined surface area of the membrane to the mediumbeing examined. On the other side, the through holes 174, 174 a of theadjacent membrane seal 170, 170 a laid against the probe part 14together with the membrane and the probe body forms an elongateflow-through cell, which can be seen by reference to FIG. 4.

FIG. 4 shows the probe part 14 for receiving the unit 16, which unit iscomprised of membrane and membrane holder, in a longitudinal section a)perpendicular to the plane of the membrane, a top view b) of the surface140 of the probe part 14 lying opposite to the membrane and a sectionalview c), seen along the arrow A—A in FIG. 4a).

FIG. 4a) shows two through-holes 142, through which two screws can beinserted, with which the membrane holder 160 shown in FIG. 2 togetherwith the membrane and two of the membrane seals shown in FIG. 3 can beconnected as a assembled unit 16 with the probe 10 or as the case may beprobe part 14. The unit 16 is fittingly engaged thereby in the recess144 formed in the probe part 14. The incoming and outgoing lines 146 a)and 147 b) lead, as can be seen particularly from FIG. 4b)—in thisembodiment to the end-open surface 140 lying opposite to the membraneend, since the flow-through cell is embedded or formed in the membraneseal 170 shown in FIG. 3 and is bordered or limited by the membrane andthe surface 140 by the seal passageway 174. The acceptor medium flowsduring measurement through the incoming line 146 a or b into the probe,then through the flow-through cell lying in front of the illustrationplane of FIG. 4, and then out of the probe through the outgoing line 146b or a.

The connections for the incoming and outgoing lines 146 a, 146 b areshown in FIGS. 5a (cross sectional view) and 5 b (top view) and arelocated in the probe cap 18 as fittings in the connection lines 148 aand 148 b for accepting and transferring the acceptor medium, forexample to the measurement unit.

Finally, FIG. 6 shows two different embodiments of the inventive probein assembled condition in a reactor 200, and more specifically first asa compact probe 10 a and second as a probe 10 b with a long submersiontube 12 (with the same construction components indicated using the samereference numbers). The probe can be adapted to the most variousassembly situations and demands.

What is claimed is:
 1. A probe (10) for collection of a sample of ananalyte situated in a fluid medium, comprising a probe body (12)including a probe part (14), a membrane holder (160) located at theprobe part (14), a membrane unit comprising an analyte permeablemembrane, the membrane introduced between first and second membraneseals (170), said membrane unit being provided between said probe part(14) and said membrane holder (160), wherein the membrane unit via themembrane holder (160) is releasably and sealingly securable to the probepart (14), wherein said first and second membrane seals (170) haverespectively one through-hole (174), wherein said first membrane sealthrough hole faces the membrane and the probe body part (14), andwherein said second membrane seal through hole faces the membrane andthe membrane holder (160), a flow-through cell defined in said probe(10) and located behind the membrane, at least one incoming line and oneoutgoing line leading to and from the flow-through cell, wherein saidmembrane holder (160) and said membrane unit form an unit replaceablyremovable from the probe part (14), and wherein the membrane holder(160) forms a gland and in association with the through holes (174) ofthe membrane seals (170) exposes only a predetermined limited surfacearea of the membrane covering the flow-through cell.
 2. A probe (10)according to claim 1, wherein said flow-through cell extends along themembrane in an elongate shape.
 3. A probe (10) according to claim 2,wherein said flow-through cell is formed as a channel bordered by themembrane and optionally an associated membrane seal (170).
 4. A probe(10) according to claim 2, wherein said incoming and outgoing lines areprovided at the side of the elongate flow-through cell opposite the sideexposed to the membrane.
 5. A probe (10) according to claim 1, whereinsaid probe (10) is tube-shaped, wherein the flow-through cell, and anunit formed by the membrane and the membrane holder (160) are providedat one end of the tube-shaped probe, and wherein the incoming endoutgoing line(s) lead to connections at the other end of the tube-shapedprobe.
 6. A probe (10) according to claim 1, wherein the membrane andthe membrane holder (160) form a unit that is screwed into the probe(10).
 7. A probe (10) for collection of a sample of an analyte situatedin a fluid medium, comprising a probe body (12) including a probe part(14), a membrane holder (160) located at the probe part (14), a membraneunit comprising an analyte permeable membrane, the membrane introducedbetween first and second membrane seals (170), said membrane unit beingprovided between said probe part (14) and said membrane holder (160),wherein the membrane unit via the membrane holder (160) is releasablyand sealingly securable to the probe part (14), wherein said first andsecond membrane seals (170) have respectively one through-hole (174),wherein said first membrane seal through hole faces the membrane and theprobe body part (14), and wherein said second membrane seal through holefaces the membrane and the membrane holder (160), a flow-through celldefined in said probe (10) located behind the membrane, at least oneincoming line and one separate outgoing line leading to and from theflow-through cell, for conveying an acceptor medium through theflow-through cell for accepting said analyte passing through saidmembrane, wherein said membrane holder (160) and said membrane unit forman unit replaceably removable from the probe part (14), and wherein themembrane holder (160) forms a gland and in association with the throughholes (174) of the membrane seals (170) exposes only a predeterminedlimited surface area of the membrane covering the flow-through cell.